Multiplex telegraph system



Aug. 4, 1942. J. A. SPENCER MULTIPLEX TELEGRAPH SYSTEM- 4 Filed April29. 1939 2 Sheets-Sheet 2 I Il Q l www@ n lllllJ u l u u UA INH cw Y

Patented ug. 4, 1942 MULTIPLEX TELEGRAPH SYSTEM James A. Spencer,Teaneck, N. J., assignor to Radio Corporation of America, a corporationof Delaware Application April 29, 1939, Serial No. 270,716

8 Claims.

This invention relates to multiplex telegraph systems and moreparticularly to an arrangement of synchronous telegraph apparatussuitable for multi-channel communications where one at least of thechannels is allocated to automatic Morse telegraphy and two or morechannels are allocated to equal length printing telegraph codesignalling.

It is an object of my invention to provide multiplex telegraph apparatusof the character described in which the signalling time may be suitablydivided as between different channels while permitting convenient timeintervals to elapse between the transmission of successive complete codesignals to one particular channel, which time intervals may be utilizedfor operating a tape feeding device at the transmitter and forperforming the essential printing operations at the receiver.

Various other objects and advantages of my invention will be mademanifest from a reading of the following description and from theaccompanying drawings in which Figure 1 shows diagrammatically apreferred circuit arrangement interconnecting the various units to beemployed at a transmitting station, and

Fig. 2 shows, also diagrammatically, a preferred embodiment of apparatusunits and interconnecting circuits to be employed at a receivingstation.

Referring rst to Fig. 1, I show conventionally two similar tapetransmitters for use on respectively diiferent channels A and B of amultiplex system. These tape transmitters are well known in the art andit is, therefore, unnecessary to show them in detail, other than thecontact devices which are controlled by a perforated tape, and themagnet I by which the mechanism is actuated, step by step.

The actual allocation of time units to the different channels ispreferably made by means of two distributors D and 6. The latter is hereshown in developed form and comprises a solid ring I and a segmentedring adjacent thereto. The segmented ring includes twenty-one conductivesegments a., b and c, which are separated from one another by insulationsegments. Seven of these segments, designated c are idle segments,because when the brush 8 passes over them time is alotted to a Morsetape transmitter as shown at 9.

My invention is particularly well adapted to the use of uniform lengthprinter signals having seven units, The perforated tape transmitters Aand B have, therefore, been shown each with seven CII contact devicescorresponding with seven rows of 5' perforations in the tape. Thetape-controlled transmitting mechanism, as is Well known in the art, isadapted to move the contact elements I0 into engagement with either amarking or a spacing conductor thereby to compose the elements of a codesignal. As shown in the drawings, the marking side of the A transmitteris connected to the positive terminal of a direct current source,whereas the spacing side is connected to the negative terminal. In orderto reverse the signals on different channels it is preferable to arrangethe marking and spacing contacts of the channel B transmitter so thatthe marking side will be negative and the spacing side will be positive.

The solid ring 'I is connected to two adjacent segments I I of amultiplex distributor. On this same distributor is a third segment I2which is fed with marking and spacing impulses derived from a Morse tapetransmitter 9. The brush I3 of the multiplex distributor is driven by amotor 5. The motors 3, 4 and 5 are maintained in synchronism with oneanother due to the fact that they are all driven from the constantfrequency source 2. The driving gear supplied to the brushes 8 and I3respectively is such, however, that successive contacts on distributor 6will be made segment by segment in synchronism with successive contactsof the brush I3 on the two segments II and the one segment I2. In otherwords, the brush 8 will rotate through one complete cycle over its 2|contactk segments, while brush I3 makes three and one-half revolutions.This is because the brush I3 is double ended and one-half revolution issuicient to cover three segments.

The brush I3 is connected to a keyer of con- Ventional type as used, forexample, in radio telegraph circuits. The keyer, in turn, controls aradio transmitter as shown. The apparatus which I prefer to employ inthe unit labeled Locking tone keyer (Fig. 1) is electronic in action.One such unit is shown in United States Patent 2,086,351 to J. L.Callahan, where in Fig. 1 a keying circuit is indicatedby referencenumeral 26. It comprises two discharge tubes which are mutuallyinteracting. One of these tubes is renderedy conductive by a positiveimpulse, and it automatically blocks the other tube. In response to anegative impulse, however, the latter tube is rendered conductive, andthe iirst tube is automatically blocked. The cathodes of these tubes aregrounded, and this provides a reason for grounding a mid-point in thedirect current source shown at the extreme left of Fig. 1 in the instantapplication.

When the distributors 6 and D have been correctly phased with respect toone another, it will be seen that while the brush 8 passes over each ofthe segments c a signal may be sent, not through these segments c, butdirectly into segment I2 of the multiplex distributor D from the Morsetransmitter 9. Intervening between certain of the segments c ofdistributor 6 are segments a which are allocated respectively to each ofthe seven units of the channel A transmitter. These segments aretraversed successively by the brush 8 and simultaneously the brush I3 ofthe multipleX distributor passes over one or the other of the segments II. After all of the elements of the code signal for channel A have beentransmitted, the elements of a signal for channel B may be transmittedthrough segments of distributor 6 marked b and thence to segments I I ofthe multiplex distributor. The time intervening between successivetransmission of different code signals by one channel is utilized forfeeding the perforated tape forward so as to sense the perforations ofthe next character signal.

The operating magnet I for each tape transmitter is energized at regularintervals so as to carry out the tape sensing function and to feed thetape forward step-by-step. The timing of the operation of each magnet Iis accomplished by means of a distributor ring I4 in cooperation with abrush i5 which rotates synchronously with brush and is preferablymounted on the same shaft therewith. Segment I6, when contacted by brushl5 (after the passage of brush 8 over the code unit segments a) feedscurrent from the source I8 to the magnet I which controls the operationof channel A transmitter. Likewise, when segment l1 is contacted bybrush I5 (after the passage of brush 8 over the code unit segments b)feeds current to the other magnet I which controls the operation ofchannel B transmitter.

Referring now to Fig. 2, which comprehends the various apparat-us unitsand circuit connections preferably employed at a receiving station, Ishow therein a radio receiver 2! which may be located at any convenientpoint preferably in an outlying section where a multiplicity of radioantennas may be set up at points spaced apart for the sake of diversityreception. Only one such antenna and its associated receiver are hereshown, as it is well understood how the signals from a plurality ofreceivers may be combined and transmitted through one interconnectingline to a traffic terminal station. The interconnecting line is shown inthe drawings as a dot and dash line 22, at the two terminals of whichcoupling transformers 23 are located. At the traffic terminal station Ipreferably locate an amplifier and rectifier 24, the output from whichis fed directly to a coupling unit 25 and by a branch circuit to asynchronous correction unit 26. The details of the units 24. 25 and 26are shown and described in United States Patent #2,062,009, grantedNovember 24, 1936, to R. E. Mathes, and in United States Patent#2,086,351, granted July 6, 1937, to J. L. Callahan.

lThe output from the coupling unit 25 is fed to a multiplex distributorbrush 21 which is double-ended and which engages with three segments 26,29 and 3l! successively. The brush 21 is driven by a motor 3l which ispowered from a constant frequency alternating current source 22.Synchronism and correct phasing of the brush 21 is, however, maintainedby means of a correction motor 33 which is geared to the stator of themotor 3l and is reversibly rotated in response to occasional currentsfrom the synchronous correction unit 26 delivered at such times as it isnecessary to correct the phasing of the brush 21. These times forapplying correction are determined by the action of a brush 34 whichcooperates with two segments 35 and 36 of a correction distributor ringThe circuits closed alternatively by the wiping of brush 34 overcontacts 35 and 36 in cooperation with the timing of the receivedsignals, as fed into the synchronous correction unit through theconductors 31, determine the action of the synchronous correction unitin controlling the correcting motor 33. The details of thissynchronizing function are explained in the foresaid Patent #2,062,009.

Still another set of distributor rings and brushes is mounted on theshaft which is driven by the motor 3l. This set is indicated generallyat 38 and is more fully explained in United States Patent No. 2,194,509,granted March 26, 1940, to R. E. Mathes. By means of the square waveoutput from the distributor 38 an alternating current is generatedwithin the apparatus unit 39, termed an auto base driving source. Thissource supplies alternating current to one or more auxiliary synchronousmotors such as that shown at 40. This particular motor 49 drives aprinter code distributor represented generally at 4I and constitutingtwo distributor rings one of which, 42, is solid and the other of whichis preferably composed of twenty-one conductive segments spaced apart byinsulation or gaps. A constant ratio is maintained as between therevolutions of the brush 43 over the rings of the distributor 4I and therevolutions of the distributor brush 21. This ratio is such that thebrush 21 contacts successively with the segments 28, 29 and 30 at thesame speed as the brush 43 contacts with adjacent segments a and c or band c. Since the brush 21 is double-ended each of the segments 28, 29and 39 is contacted twice per revolution of the multiplex channeldistributor. It is, therefore, necessary for this brush 21 to rotatethree and one-half times per revolution of the brush 43 in order toproduce twenty-one different paths through the successive segments ofthe distributor 4I. The distributor segments marked c are inactive sincethey correspond in time with the passage of the brush 21 over itssegment 28, this segment being appropriate to a Morse recorder circuitwhich is independent of the printer channels but which shares time onthe multiplex channel between two radio stations.

interposed between the distributor segment 28 and the Morse recorder 44is a so-called locking circuit 45 the output from which constitutesmarking and spacing signals which are fed to the Morse recorder 44. Thedetails of the locking circuit are shown and described in United StatesPatent #1,844,950, granted February 16, 1932, to J. L. Finch. Thepurpose of this locking circuit is to prolong the impulses applied assignals to the Morse recorder and to rebuild these signals into a squarewave in response to the eifective center portions of the receivedsignals which are selected by the small arc of the distributor segment28.

A similar locking circuit 41 is fed with printer code signal elementsfrom the distributor segments 29 and 39. The relay 46 thus responds tomarking and spacing elements of the printer code signals. Positive andnegative impulses are applied to the solid distributor ring 42 andthence successively through the several active segments a and b of theprinter distributor 4I. This process of distribution of the printer codesignals provides for individual actuation of different ones of thedecoding magnets in the printer. Seven of these magnets designated 49are shown in one group which is appropriate to and which operates thetype selectors in a printer for channel A. These magnets arerespectively controlled by impulses applied to the segments a. Similarlyanother group of decoding magnets 50 is associated with an individualprinter' for channel B. These magnets are fed with impulses as appliedthereto by the segments b of the distributor 4|.

Still another distributor ring 5| has a brush 53 rotating thereover,this brush and the brush 43 being preferably mounted on the same shaft.The purpose of the distributor 5| is to initiate local printer operatingimpulses following the reception of each full code signal. Thus asegment 52 is contacted by brush 53 immediately following the passage ofbrush 43 over segments a. At this time the printer control magnet 54 forchannel A printer is actuated. Likewise, after the brush 43 has passedover segments b, then brush 53 reaches segment 55 and impresses animpulse upon the printer magnet 5B for actuating the channel B printer.

The embodiment herein described operates in such a manner that theprinter for channel A is caused to effect a printing operation whilecode signals are being received applicable to channel B, and vice versa.It is evident that, preceding each pair of printer code signal units asassigned to the multiplex distributor segments 2B and 29, time isallotted to the Morse code recorder, the signals for which are receivedon the multiplex distributor segment 28. There is, therefore, no losttime in transmission of signals for three separate communications on thethree respective channels of the multiplex systemy A further advantageto be derived from the circuit arrangement as herein shown and describedis that of iiexibility of disposition of the various operating units.This advantage is brought about by the employment or synchronous motors,such as the motor 49, whose driving source is maintained in synchronismwith the received signals by the square wave former 38 in cooperationwith the auto base driving source 39. Hence it is possible to locate themultiplex distributor at one convenient point, then to locate the codeunit distributor 4| at another convenient point and each of therecording or printing units such as 44, 64 and 65 where they may beproperly attached for the reception of messages.

The particular system herein disclosed is one that is well adapted tothe operation of 'Y-unit printers such as shown and described in thefollowing U. S. patents:

No. 2,183,147, granted December l2, 1939, to Moore and Mathes; Nos.2,153,737 and 2,231,397, granted April 1l, 1939, and February l1, 1941,respectively, both to J. A. Spencer.

To those skilled in the art various modifications of the invention maybe made without departing from the spirit and scope of the inventionitself. Such scope is dened and limited only in accordance with theclaims.

I claim:

1. In a multiplex telegraph system, a transmitting station comprising amultiple channel distributor, an automatic Morse code transmitter incircuit with one of the segments of said distributor, a plurality ofother segments on said distributor, a plurality of equal-length codesignaling devices, each alternatively connectable to said othersegments, a second transmitting distributor having segments individualto the respective code units of a plurality of signals successivelytransmittable first by one and then by another said device, a receivingstation having a multiplex channel distributor and a code-unit analyzingdistributor, means for causing signals to be sent from said transmittingstation to said receiving station, means for maintaining all of saiddistributors in synchronism, and means including circuit connectionsbetween the two distributors of said transmitting station, also betweenth-e two distributors of said receiving station, whereby the dot unitsof Morse code signals are interspersed between portions of each equallength code signal, the transmission and reception of successivecomplete equal length code signals being in accordance with successiveallotments of channel time to the respective equal length code signalingdevices.

2. A multiplex telegraph system wherein the dot mark of the individualchannel is used as the fundamental time unit, said system comprising, atransmitting terminal including a Morse code keyer and two sets of equallength printer code keyers, a distributor having a plurality oi?segments successively traversed by a brush at dot mark frequency, saidsegments being connected individually to different code-unit portions ofeach of said keyer sets, and having idle segments interspersed betweenthe connected segments, means including another distributor forperiodically connecting said Morse code keyer to the output side of thetransmitting terminal during the passage of said brush over each of saididle segments, a receiving terminal having an arrangement ofdistributors equivalent to that at the transmitting terminal incombination with a Morse recorder and two printers each operative fromsignals received and assigned thereto by said arrangement ofdistributors, and means including a signaling channel whereby said Morserecorder and said printers are rendered responsive to signals sent outfrom said transmitting terminal. Y

3. A system in accordance with claim 2 and including means locallycontrolled at the receiving terminal for timing the actuation of each ofsaid printers subsequent to the assignment there- 'to of the full quotaof code signal elements for selecting and printing a given character.

4. A system in accordance with claim 2 and including means drivensynchronously with said distributors for suitably timing the actuationof each of said printer code keyers.

5. A multiplex transmitting and receiving system comprising incombination, a three-channel segmented distributor and a multiple dotunit segmented distributor, each of said distributors having a collectorring and a brush for bridging the collector ring in circuit with itssegments successively, a Morse code transmitter connected to anappropriate one of the segments of the first said distributor, a printercode transmitter having a plurality of marking-or-spacing unit selectorseach connected to an appropriate segment of the second said distributor,a second printer code transmitter having selectors like- Wise connectedto others of the segments of the second said distributor, an electricalconnection between the collector ring of the second said distributor andtwo otherwise unappropriated segments of the iirst said distributor,transmitting means under control of impulses derived from the collectorring of the rst said distributor, means for causing the brushes of thetwo distributors to traverse their segments simultaneously and at thesame rate of progression, a plurality of recording and printing unitslocated at a receiving terminal, means including a complementary set ofdistributors at said receiving terminal having connections to saidrecording and printing units corresponding with those at thetransmitting terminal, means rendering said recording and printing unitsresponsive to signals sent out by said code transmitters, and means formaintaining synchronism between all said distributors.

6. A multiplex transmitting and receiving system comprising incombination, a plurality of code signal keying units located at atransmitting station, a plurality of recording and printing unitslocated at a receiving station, a commuications channel interconnectingthe two stations, channel time distributors at both stations, means formaintaining syn-chronism and proper phasing of each distributor withrespect to the others, means at the receiving station including one ofits distributors for selecting the rst of each three successiveelementary code units of the code signals for assignment to a givenrecording unit, means at said receiving station including another of itsdistributors for allocating the remaining elemental code units of thecode signals rst to one printer unit until a single character codesignal has been fully received, and then to another printer until asubsequent character code signal has been received, and means forcausing each printer to be actuated during the time that a code signalis being assigned to the other printer.

'7. In a'multiplex telegraph system, a sending station and a receivingstation, means providing communication from the sending station to thereceiving station, means at the sending station for transmitting codesignals the elements of which are of uniform length, a plurality ofprinters at said receiving station, means for operating said printerscyclically rst to make a character selection in accordance with anassigned code signal and then to print the character selected, means forso staggering the operating cycles of said printers that the characterselecting cycle of one printer is concurrent with the character printingcycle of another printer, means at the sending station for interseprsingother signals with the code signals assigned to said printers, andresponsive means Iat said receiving station for detecting said othersignals.

8. In a multiplex telegraph system according to claim 7, the combinationtherein set forth wherein said responsive means includes means forrecording the intelligence of said other signals concurrently with theoperating cycles of said printers, the last said means being responsiveto code signal combinations of unequal length.

JAMES A. SPENCER.

